Effects of Green and Gold Kiwifruit Varieties on Antioxidant Neuroprotective Potential in Pigs as a Model for Human Adults.

Kiwifruit (KF) has shown neuroprotective potential in cell-based and rodent models by augmenting the capacity of endogenous antioxidant systems. This study aimed to determine whether KF consumption modulates the antioxidant capacity of plasma and brain tissue in growing pigs. Eighteen male pigs were divided equally into three groups: (1) bread, (2) bread + Actinidia deliciosa cv. 'Hayward' (green-fleshed), and (3) bread + A. chinensis cv. 'Hort16A' (yellow-fleshed). Following consumption of the diets for eight days, plasma and brain tissue (brain stem, corpus striatum, hippocampus, and prefrontal cortex) were collected and measured for biomarkers of antioxidant capacity, enzyme activity, and protein expression assessments. Green KF significantly increased ferric-reducing antioxidant potential (FRAP) in plasma and all brain regions compared with the bread-only diet. Gold KF increased plasma ascorbate concentration and trended towards reducing acetylcholinesterase activity in the brain compared with the bread-only diet. Pearson correlation analysis revealed a significant positive correlation between FRAP in the brain stem, prefrontal cortex, and hippocampus with the total polyphenol concentration of dietary interventions. These findings provide exploratory evidence for the benefits of KF constituents in augmenting the brain's antioxidant capacity that may support neurological homeostasis during oxidative stress.

Actinidin reduces gluten-derived immunogenic peptides reaching the small intestine in an in vitro semi-dynamic gastrointestinal tract digestion model.

Actinidin, a cysteine protease in green kiwifruit (Actinidia deliciosa), has been identified as a potential enzyme to hydrolyse gluten within the lumen of the gastrointestinal tract (GIT). The present study aimed to further evaluate the effect of purified actinidin sourced from green kiwifruit on the digestion of gluten and the release of immunogenic peptides during GIT digestion using an in vitro semi-dynamic GIT digestion model. Purified gluten was digested for 180 min with or without actinidin and subsequently analysed for free amino groups (o-phthaldialdehyde) to determine the degree of hydrolysis (DH), gluten R5 epitopes (ELISA), and peptide profiles (mass spectrometry). Strong interactions were observed between treatment (GIT digestion with or without actinidin) and digestion time for the DH of gluten (P < 0.01), amount of free amino groups released into the small intestine (P < 0.01), and amount of gluten epitopes present in the small intestine (P < 0.001). The rate of increase of DH of gluten and the amount of R5 epitopes present in the small intestine during the first 30 min of GIT digestion with actinidin was 0.3%/min and 4.8 ng/g of gluten respectively, whereas it was 0.01%/min and 60.9 ng/g of gluten respectively without actinidin. These results were corroborated by untargeted peptidomics, with a 1.5-fold lower number of known immunogenic epitopes reaching the small intestine at 30 min of GIT digestion when actinidin was present compared to the control. Present results demonstrate that actinidin enhanced the rate of proteolysis of gluten and reduced the number of immunogenic gluten epitopes reaching the small intestine during simulated semi-dynamic GIT digestion.

Rapid proteolysis of gluten-derived immunogenic peptides in bread by actinidin in a combined in vivo and in vitro oro-gastrointestinal digestion model.

This study aimed to determine the ability of actinidin, a cysteine protease in green kiwifruit (Actinidia deliciosa), to hydrolyse wheat proteins and gluten-derived immunogenic peptides from a commonly consumed food matrix (bread) using a combined in vivo and in vitro oro-gastrointestinal tract (GIT) model. A chewed and spat composite bolus of bread was in vitro digested with or without purified actinidin using a human gastric simulator (HGS). Gastric digestion was conducted for 150 min with gastric emptying occurring at different time points. Emptied samples were immediately digested under simulated small intestinal conditions. Gastric and small intestinal aliquots were collected to quantify peptide profiles and nine marker immunogenic peptides (by untargeted and targeted mass spectrometry, respectively), R5 epitopes (by monoclonal antibody-based competition assay), and free amino groups released by digestion (by the o-phthaldialdehyde method). There was a significant effect (P < 0.05) of actinidin and digestion time on the hydrolysis of wheat proteins and the amount of gluten R5 epitopes of that material emptying the HGS. Actinidin accelerated 1.2-fold the gastric hydrolysis of wheat proteins during the first 20 min of digestion, which was reflected in a faster (5.5 µg min-1) reduction in the evolution of R5 epitopes. Actinidin accelerated (P < 0.05) the rate of disappearance of most of the immunogenic marker peptides. For example, in the first 20 min of small intestinal digestion, the 33-mer peptide decreased (P < 0.05) 2-fold faster (0.25 vs. 0.12 µg g-1 of bread per min) in the presence of actinidin than in the control. Untargeted peptidomics showed actinidin decreased the amounts of known immunogenic peptides in the simulated small intestinal digestion. These findings demonstrated that actinidin accelerates the hydrolysis of wheat proteins and known gluten immunogenic peptides in a commonly consumed food matrix (bread) in a combined in vivo and in vitro oro-GIT digestion model.

The kiwifruit enzyme actinidin enhances the hydrolysis of gluten proteins during simulated gastrointestinal digestion.

This study investigated the effect of actinidin, a cysteine protease in kiwifruit, on the hydrolysis of gluten proteins and digestion-resistant gluten peptides (synthetic 33-mer peptide and pentapeptide epitopes) under static simulated gastrointestinal conditions. Actinidin efficacy in hydrolysing gliadin was compared with that of other gluten-degrading enzymes. Actinidin hydrolysed usually resistant peptide bonds adjacent to proline residues in the 33-mer peptide. The gastric degree of hydrolysis of gluten proteins was influenced by an interaction between pH and actinidin concentration (P < 0.05), whereas the pentapeptide epitopes hydrolysis was influenced only by the actinidin concentration (P < 0.05). The rate of gastric degree of hydrolysis of gliadin was greater (P < 0.05) by actinidin (0.8%/min) when compared to papain, bromelain, and one commercial enzyme (on average 0.4%/min), while all exogenous enzymes were able to hydrolyse the pentapeptide epitopes effectively. Actinidin is able to hydrolyse gluten proteins under simulated gastric conditions.